first stab at eip155:0 lang in eip155/caip2.md

[bumblefudge]

Discussions coming out of the CAIP-25 syntax overhaul conversation made me realize this should've been specified a long time ago!

[kdenhartog]

Has there been any thought about the backwards compatibility with this yet? E.g. I don't think you'll be able to drop and replace this in a EIP-712 signature because conformance there expects the chainId is a JSON integer. This is probably something that will need to be informed by implementer feedback taking in mind that stuff like this led to many wallets having responsible disclosure bugs reported around this: https://www.coinspect.com/blog/chainid-eip-712-implementation-issue/

[bumblefudge]

Has there been any thought about the backwards compatibility with this yet?

Sort of-- I take your point about "chainId":0 maybe throwing wallets, but as the link you provided states, the problem is that wallets aren't checking, not that they've overvalidating 😅 . this is kind of directional/aspirational, though, it would only really come up as an issue for wallets if dapps and SDKs start using it, and I'm not sure it would ever come up for 712 signs... CAIP-25 is probably the only place it would come up for now